EP1998435B1 - Method and system for estimating rotor angular position and rotor angular velocity at low speeds or standstill - Google Patents

Method and system for estimating rotor angular position and rotor angular velocity at low speeds or standstill Download PDF

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EP1998435B1
EP1998435B1 EP08251107.2A EP08251107A EP1998435B1 EP 1998435 B1 EP1998435 B1 EP 1998435B1 EP 08251107 A EP08251107 A EP 08251107A EP 1998435 B1 EP1998435 B1 EP 1998435B1
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EP1998435A3 (en
EP1998435A2 (en
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Jun Hu
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Hamilton Sundstrand Corp
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Hamilton Sundstrand Corp
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02PCONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/06Rotor flux based control involving the use of rotor position or rotor speed sensors
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02PCONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/14Estimation or adaptation of machine parameters, e.g. flux, current or voltage
    • H02P21/18Estimation of position or speed

Description

    BACKGROUND OF THE INVENTION
  • This invention relates to rotor angular position and velocity sensing systems for mechanical shaft sensorless control of dynamoelectric machines, and more particularly to an improved system for resolving the position and velocity of a rotor for a dynamoelectric machine using an estimate of extended rotor flux.
  • In some vehicles, including some aircraft, a motor may be utilized both as a motor and as a generator. Because of this dual function, the motor may be called a dynamoelectric machine. A typical motor comprises a stationary stator, and a rotating rotor. In some motors, it is necessary to detect a position of a rotor in order to sustain operation of the motor. Determining a rotor position typically requires a shaft position sensor. It is desirable to eliminate a mechanical shaft sensor to reduce cost and improve reliability.
  • Some methods of sensorless rotor position detection include the back EMF method, which determines rotor position based on voltage, the signal injection method, which injects high frequencies into a system, and the method discussed in U.S. Patent No. 7,072,790 which uses flux to determine rotor position. It is desirable to improve the method U.S. Patent No. 7,072,790 for applications operating at low speeds or at a standstill.
  • SUMMARY OF THE INVENTION
  • The present invention relates to a method of estimating rotor angular position and rotor angular velocity for a dynamoelectric machine as claimed in claim 1, and to a control for estimating an initial rotor angular position and a rotor angular velocity for a dynamoelectric machine from a standstill as claimed in claim 8.
  • A method and system for estimating an angular position and an angular velocity of a rotor in a dynamoelectric machine measures an AC current and a potential for each of a plurality of windings coupled to a stator of the dynamoelectric machine, transforms the measured currents and potentials to a stationary frame to produce transformed currents and transformed potentials, and processes the transformed currents and transformed potentials to produce a first intermediate signal and a second intermediate signal. The first intermediate signal and the second intermediate signal are cross-coupled and processed to obtain a first extended rotor flux value and a second extended rotor flux value. The first extended rotor flux value and the second extended rotor flux value are applied to a phase lock loop to derive an estimated rotor angular position and an estimated rotor angular velocity for the dynamoelectric machine.
  • These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description, and which describe certain embodiments of the invention by way of example only.
  • BRIEF DESCRIPTION OF THE DRAWINGS
    • Figure 1 illustrates a block diagram of a mechanical sensorless rotor angular position and velocity sensing system.
    • Figure 2 illustrates a phasor diagram of electrical parameters related to extended rotor flux.
    • Figure 3 illustrates a block diagram of operations performed within the system of Figure 1 to calculate a first extended rotor flux value and a second extended rotor flux value.
    • Figure 4 illustrates a block diagram of how a microprocessor of Figure 1 uses a phase lock loop (PLL) to obtain an estimated rotor angular position and an estimated rotor angular velocity.
    • Figure 5 illustrates how a stationary frame of the system of Figure 1 aligns with multiple phases of AC.
    • Figure 6 illustrates an initial stator voltage and an initial rotor position as a function of time.
    DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
  • As shown in Figure 1, the rotor angular position and velocity sensing system 10 comprises a motor 12 that is able to operate as a starter to start an engine 14, or as a generator to power a load (not shown). Because of this dual function, the motor 12 may be called a dynamoelectric machine. In one example, the motor 12 is a brushless motor that requires a controller to know a position of its rotor to operate.
  • To start the motor 12, an AC power supply 16 provides an AC voltage along supply lines 18 to a rotating exciter 19. In the example of Figure 1, the AC power supply 16 provides three phases of AC power, however it is understood that other numbers of phases of AC power could be provided. The rotating exciter is connected to a shaft 21 that is also connected to the motor 12 and the engine 14.
  • The AC voltage from the supply lines 18 induces an AC voltage along motor terminals 20a, 20b, and 20c. The induced voltage causes a current to flow through an output filter 22. A microprocessor 24 measures a voltage 26 and a current 28 from each of the terminals 20a, 20b, and 20c. A position and speed estimator 30 uses the voltage and current measurements to estimate a flux of the motor 12 and to estimate a rotor position 32 and a rotor angular velocity 34.
  • Once the estimated rotor position 32 and estimated rotor angular velocity 34 have been calculated, an inverter 38 is turned ON. The microprocessor 24 processes the estimated rotor position 32 and estimated rotor angular velocity 34 to control a pulse width modulated (PWM) generator 36. Inverter 38 is coupled to the PWM generator 36 and converts a DC voltage from DC voltage supply lines 40 to AC. This voltage enables AC to flow through the output filter 22, which improves power quality by filtering out harmonics and reducing electromagnetic interference (EMI). The AC from the terminals 20a, 20b, and 20c then flows to a stator of the motor 12 to sustain operation of the motor 12.
  • Figure 1 illustrates how the microprocessor 24 processes the estimated rotor position 32 and estimated rotor angular velocity 34 to control the inverter 38. An abc to d-q frame transformer 42 uses the estimated rotor position 32 to transform the current measurements 28 to a rotating d-q frame to obtain current values Id and Iq. A torque current profile generator 44 uses the estimated rotor angular velocity 34 to lookup reference current values Id* and Iq*. Comparators 45 and 46 compare the transformed Id and Iq values to reference current values Id* and Iq* to determine differences ΔId and ΔIq between the transformed values and the reference values.
  • Proportional and integral (PI) regulators 47 and 48 process the differences ΔId and ΔIq using proportional and integral gains, and transmit an output signal to d-q to alpha-beta frame transformer 50, which converts the output into a stationary α -β frame to produce Valpha* and Vbeta* signals which are transmitted to the PWM generator 36. The PWM generator then controls the inverter 38 accordingly to produce a desired AC voltage.
  • The output filter 22 comprises an inductor and a capacitor (not shown) in each phase. An input current Iinvt flows from the inverter 38 along the windings 23 a, 23b, and 23c to the output filter 22, and an output current Is flows from the output filter 22 along the terminals 20a, 20b, and 20c to the motor 12. The current flowing through the capacitor can be calculated by the following equation: I ^ c = C V s t
    Figure imgb0001
    • where Îc is an estimated capacitor current; and
    • Vs is one of the voltage measurements 26.
    A motor current can then be calculated using the following equation: I s = I invt - I ^ c
    Figure imgb0002
    • where Is is the calculated motor current; and
    • Iinvt is the inverter output current.
    Equations 1 and 2 apply to all three phases A, B, and C corresponding to the three windings 20a, 20b, and 20c.
  • The voltage measurements 26 and current measurements 28 are measured from each of the three terminals (20a, 20b, 20c) and each of the three windings (23a, 23b; 23c) in an a-b-c frame. The current measurement 28 is a measurement of the inverter output current Iinvt. A flux estimation is implemented in an alpha-beta (α-β) stationary frame. The relationship between the α-β frame and the a-b-c frame is described in the following equation: f α f β = 2 3 1 - 1 2 - 1 2 0 3 2 - 3 2 f a f b f c
    Figure imgb0003
    • where f can be replaced with voltage, current, or flux;
    • α, b, and c represent the phases of current on the terminals 20a, 20b, and 20c in the a-b-c frame; and
    • α and β represent axes of the α-β frame.
  • The stationary α-β frame is a two phase frame and is a necessary step in calculating flux. Equation #3 is used to determine an α-axis voltage Vα, a β-axis voltage Vβ, an α-axis current Iα, and a β-axis current Iβ.
  • The following equation can then be used to determine an extended rotor flux in the α-β stationary frame: λ ext_α λ ext_β = 1 s V α V β - R s 0 0 R s I α I β - L q 0 0 L q I α I β
    Figure imgb0004
    • where λ ext is an alpha extended rotor flux;
    • λ ext is a beta extended rotor flux;
    • Rs is a stator resistance;
    • Lq is a q-axis inductance; and
    • 1/s is an integrator.
    Equation #4 can be used to determine flux in both salience and non-salience motors. As shown in equation #4, an integrator 1 s
    Figure imgb0005
    is required to calculate extended rotor flux. The integrator 1 s
    Figure imgb0006
    is an operator, not a variable, s being a Laplace operator. One problem that may arise when using a pure integrator, such as " 1 s " ,
    Figure imgb0007
    is a DC drift problem, in which a small DC component in an AC signal can cause a substantial error in a flux determination. To avoid the DC drift problem associated with a pure integrator, lag functions, such as 1 s + ω i
    Figure imgb0008
    and ω i s + ω i ,
    Figure imgb0009
    may be used, as shown in the following equation: λ ext_α λ ext_β = 1 ω i s + ω i - ω i s + ω i 1 ω i s + ω i V α V β - R s 0 0 R s I α I β - L q 0 0 L q I α I β
    Figure imgb0010
    • where ωi is a selected corner frequency.
    Selected corner frequency ωi may be fixed or it may be adjustable.
  • Figure 2 illustrates a phasor diagram in the rotating d-q frame. Figure 2 illustrates the relationship between extended rotor flux and back EMF.
  • A flux λs in the stator of the motor 12 is represented by a phasor 60. A stator current Is is represented by a phasor 62. A stator potential Vs is represented by a phasor 64. A phasor 66 represents Is*Lq where Lq is a q-axis rotor inductance. A vector sum of the phasor 60, representing λs, and the phasor 66, representing Is*Lq, is an extended rotor flux λext, which aligns with the d-axis of the d-q frame, and is represented by a phasor 67.
  • A back electromotive force (EMF) Es is represented by a phasor 68. As shown in Figure 2, the back EMF Es is perpendicular to the stator flux λs . The back EMF Es , represented by the phasor 68, is a vector sum of the stator potential Vs represented by phasor 64 and stator resistance potential drop Is*Rs represented by a phasor 70, where Rs is the stator resistance.
  • An extended back electromotive force (EEMF), Eext , in the stator is represented by a phasor 72, and aligns with the q-axis of the d-q frame. Is*Xq , where Xq is a q-axis stator reactance, is represented by a phasor 74. The extended back EMF represented by phasor 72 is a vector sum of Es represented by phasor 68 and Is*Xq represented by a phasor 74.
  • Figure 3 illustrates a block diagram of the flux estimation algorithm shown in equation #5. As shown in Figure 3, a transformed measured current Iα for the α -axis on a signal path 80 is multiplied by the stator resistance Rs 82 to produce Iα *Rs on a signal path 84. A summer 86 subtracts Iα * Rs on the signal path 84 from the transformed potential V α on a signal path 88 to produce V α-(Iα*Rs ) on a signal path 90. Vα- (Iα *Rs ) on the signal path 90 is multiplied by a 1 s + ω i
    Figure imgb0011
    first lag function 92 to produce first intermediate signal 1 s + ω i V α - I α * R s
    Figure imgb0012
    on a signal path 93. 1 s + ω i V α - I α * R s
    Figure imgb0013
    on the signal path 93 is multiplied by a ω i s + ω i
    Figure imgb0014
    second lag function 94 to produce ω i s + ω i V α - I α * R s
    Figure imgb0015
    on a signal path 95.
  • Additionally, a transformed measured current I β for the β-axis on a signal path 96 is multiplied by the stator resistance Rs 98 to produce Iβ *Rs on a signal path 100. A summer 102 subtracts Iβ *Rs on the signal path 100 from the transformed potential Vβ on a signal path 104 to produce Vβ-(Iβ*Rs ) on a signal path 106. Vβ -(Iβ*Rs ) on the signal path 106 is multiplied by the 1 s + ω i
    Figure imgb0016
    first lag function 108 to produce second intermediate signal 1 s + ω i V β - I β * R s
    Figure imgb0017
    on a signal path 110. 1 s + ω i V β - I β * R s
    Figure imgb0018
    on the signal path 110 is multiplied by the ω i s + ω i
    Figure imgb0019
    second lag function 112 to produce ω i s + ω i V β - I β * R s
    Figure imgb0020
    on a signal path 114.
  • The transformed measured current I α for the α-axis on the signal path 80 is also multiplied by a q-axis inductance Lq 116 to produce I α *Lq on the signal path 118. A summer 120 subtracts Iα*Lq on the signal path 118 from 1 s + ω i V α - I α * R s
    Figure imgb0021
    on the signal path 93 and adds ω i s + ω i V β - I β * R s
    Figure imgb0022
    from the signal path 114 to produce 1 s + ω i V α - I α * R s + ω i s + ω i 2 V β - I β * R s - I α * L q
    Figure imgb0023
    which corresponds to the extended rotor flux on the α-axis λ ext_α on the signal path 122. The "^"notation indicates that the extended rotor flux is an estimate based on measured values.
  • Additionally, the transformed measured current Iβ for the β-axis on the signal path 96 is also multiplied by a q-axis inductance Lq 124 to produce Iβ*Lq on the signal path 126. A summer 128 subtracts Iβ*Lq on the signal path 126 from 1 s + ω i V β - I β * R s
    Figure imgb0024
    on the signal path 110 and subtracts ω i s + ω i V α - I α * R s
    Figure imgb0025
    on the signal path 95 to produce 1 s + ω i V β - I β * R s - ω i s + ω i 2 V α - I α * R s - I β * L q
    Figure imgb0026
    which corresponds to the extended rotor flux on the β-axis λ est_β on the signal path 130. Once again, the "^"notation indicates that the extended rotor flux is an estimate based on measured values.
  • As shown in Figure 3, the signal paths 95 and 114 cross-couple the signal paths 93 and 110.
  • The following equation can be used to describe the relationship between the extended rotor flux and the rotor position: λ ext_α λ ext_β = λ cos θ sin θ
    Figure imgb0027
    • where θ is the rotor position; and
    • λ is a flux amplitude.
  • Using equation #6, it would be possible to use an arctangent function to calculate a rotor position. Another option is to used a phase-locked loop (PLL) to derive position and angular velocity information.
  • Figure 4 is a block diagram illustrating how the microprocessor 24 uses a phase lock loop (PLL) to improve an estimate of rotor angular position and rotor angular velocity. The estimated α-axis extended rotor flux λ ext_α and the estimated β-axis extended rotor flux λ ext_β are applied to the signal paths 122 and 130. A multiplier 132 multiplies the estimated α-axis extended rotor flux λ ext_α with a feedback signal on a signal path 134 from a sine function 136 to produce an α-axis multiplier output signal on a signal path 138. Likewise, a multiplier 140 multiplies the estimated β-axis extended rotor flux λ ext_β with a feedback signal on a signal path 142 from a cosine function 144 to produce a β-axis multiplier output signal on a signal path 146.
  • A summer 148 subtracts the α-axis multiplier output signal on the signal path 138 from the β-axis multiplier output signal on the signal path 146 to produce a difference signal on a signal path 150. A proportional and integral (PI) regulator function 152 multiplies the difference signal on the signal path 150 by the function K p + K i s
    Figure imgb0028
    to produce a PI output signal on a signal path 154. Ki is an integral gain of the PI function 152, and Kp is a proportional gain of the PI function 152. Both Ki and Kp are constants based on a design of the system 10 as shown in Figure 1.
  • An integral function 156 multiplies the PI output signal on the signal path 154 by the function 1 s
    Figure imgb0029
    to produce an integration output signal on a signal path 158. The integration output signal on the signal path 158 is also fed into the inputs of the sine function 136 and the cosine function 144 to provide the PLL.
  • A low pass filter (LPF) function 160 multiplies the PI output signal on the signal path 154 by a third lag function ω c s + ω c
    Figure imgb0030
    to produce an estimated rotor angular velocity ω̂ on a signal line 162, where ωc is a corner or cutoff frequency of the LPF function 160. A low pass filter associated with the LPF function 160 is used to smooth out the signal on the signal line 154.
  • The integration output signal on the signal path 158 is compensated by an offset Δθ to obtain a final estimated rotor angular position θ̂ . The offset Δθ can be a lump-sum error of miscellaneous delays, including delays introduced by the lag functions 92, 108 of Figure 3, digital sampling delays introduced in measured voltage and current signals, and computation delays in the microprocessor 24 as shown in Figure 1. A lookup table 164 may be used to compensate for this phase delay Δθ. The lookup table 164 generates a suitable phase delay Δθ on a signal path 166, and a summer 168 subtracts the phase delay Δθ from the integration output signal on the signal path 158 to produce the estimated rotor angular position θ̂ on a signal path 170.
  • Figure 5 illustrates how the α-β frame 173 comprises an α-axis 174 and a β -axis 175 that are perpendicular to each other. The α-β frame 173 aligns with a first phase 178, a second phase 180 and a third phase 182 of the system 10. A rotor 172 rotates, and its displacement from the α-axis is shown by the angle θ 184, which is the rotor angular position to be estimated.
  • When the motor 12 is at a standstill, as magnetic flux in the motor 12 changes in magnitude, a voltage is induced on the motor terminals 20a, 20b, and 20c, which can be sensed by the microprocessor 24. The induced stator voltages in the α-β frame can be described by the following equation: V α = λ s t cos θ 0
    Figure imgb0031
    V β = λ s t sin θ 0
    Figure imgb0032
    • where λs is a magnitude of stator flux; and
    • θ0 is an initial rotor position angle at standstill.
  • The measured voltage 26 can be transformed to an alpha-beta frame. The transformed measured voltages Vα and Vβ may be fed into the PLL as shown in Figure 4 to obtain the initial position angle θ0 . In that case, the voltage V α replaces the flux λ̂ ext_α on the signal path 122, and the voltage V β replaces the flux λ̂ est_β on the signal path 130 in Figure 4.
  • Figure 6 illustrates an initial stator voltage and an initial rotor position as a function of time. During startup the rotating exciter 19 is powered on by the ac power supply 16 in Figure 1. Graph 186 illustrates a line-to-line voltage for each phase of the motor 12 as a function of time, and graph 188 illustrates an estimated rotor position as a function of time in the motor 12. The inverter 38 is OFF in the time periods shown in graphs 186 and 188. A voltage 190 corresponds to a VBC line-to-line voltage, a voltage 192 corresponds to a VCA line-to-line voltage, and a voltage 194 corresponds to a VAB line-to-line voltage. An estimated rotor position θ 0 200 corresponds to an angle of the rotor 172.
  • During an initial time period 196, the AC power supply 16 is OFF, and the three voltages 190, 192, and 194 are close to zero and the estimated rotor position θ0 200 cannot be used to determine actual rotor position. Specifically, if each of the voltages does not exceed a certain threshold, the extended rotor flux values are not applied to the phase lock loop to derive an estimated rotor angular position and an estimated rotor angular velocity, and the estimated rotor angular position and estimated rotor angular velocity are designated as invalid. At time 198, the AC power supply 16 turns ON and current flows to the rotating exciter 19 through the supply line 18 in the system 10. During this period, an excitation magnetic field of the motor 12 is arising. The rising magnetic flux induces voltage at the terminals 20a, 20b, and 20c of the system 10. The magnitude of voltages 190, 192 and 194 is sufficient for the microprocessor 24 to be able to estimate rotor position θ0 200. In graph 188, from time 198 to approximately time 202 the value of θ0 remains stable, and after time 202 the value starts to fluctuate due to a decaying voltage signal as shown in graph 186. This stable period demonstrates that a rotor position can be estimated from the voltages 190, 192, and 194 during the stable time period. If the rotor angular position cannot be determined within a predetermined period of time after the rotating exciter is turned on, the system indicates a fault condition. If the rotor angular position can be determined within a predetermined period of time after the rotating exciter is turned on, the inverter is turned on.

Claims (13)

  1. A method of estimating rotor angular position and rotor angular velocity for a dynamoelectric machine (12) comprising the steps of:
    (i) measuring an AC current (28) and a potential (26) for each of a plurality of windings coupled to a stator of the dynamoelectric machine;
    (ii) transforming the plurality AC currents and potentials to a stationary frame (α-β) to produce a first transformed current, a second transformed current, a first transformed potential, and a second transformed potential;
    (iii) processing the first transformed current and the first transformed potential, and processing the second transformed current and the second transformed potential to obtain a first intermediate signal (93) and a second intermediate signal (110);
    (iv) processing the first intermediate signal and the second intermediate signal to obtain a first extended rotor flux value (122) and a second extended rotor flux value (130); and
    (v) applying the first extended rotor flux value and the second extended rotor flux value to a phase lock loop (132-158) to derive an estimated rotor angular position and an estimated rotor angular velocity for the dynamoelectric machine;
    wherein the stationary frame is a two-phase α-β frame having an α-axis and a β-taxis, and the first transformed current is Iα, the second transformed current is Iβ , the first transformed potential is Vα , the second transformed potential is Vβ , the first extended rotor flux value corresponds to the α-axis, and the second extended rotor flux value corresponds to the β-axis; and
    the step of processing the first transformed current and the first transformed potential, and processing the second transformed current and the second transformed potential to obtain a first intermediate signal and a second intermediate signal comprises the steps of:
    multiplying the first transformed current Iα and the second transformed current Iβ by a resistance Rs of the stator to produce signals Iα *Rs ,Iβ *Rs ;
    subtracting the signals I α*Rs ,I β*Rs from the first transformed potential Vα and the second transformed potential Vβ to produce signals V α-I α*Rs , V β -I β*Rs ; and
    multiplying the signals V α-I α*Rs , V β-I β*Rs by a first lag function 1 s + ω i 92 108 ,
    Figure imgb0033
    wherein ω i is a selected corner frequency for the lag function and s is a Laplace operator, to produce first intermediate signal 1 s + ω i V α - I α * R s
    Figure imgb0034
    and second intermediate signal 1 s + ω i V β - I β * R s 110 ;
    Figure imgb0035
    multiplying the transformed currents Iα,Iβ by a q-axis inductance Lq of the stator to produce signals Iα*Lq,Iβ*Lq ;
    characterised in that step (iv) comprises cross-coupling the first intermediate signal and the second intermediate signal to obtain the first extended rotor flux value (122) and the second extended rotor flux value (130); and
    in that the step of cross-coupling and processing the first intermediate signal and the second intermediate signal comprises the steps of:
    multiplying the first intermediate signal 1 s + ω i V α - I α * R s
    Figure imgb0036
    and the second intermediate signal 1 s + ω i V β - I β * R s 110
    Figure imgb0037
    by a second lag function ω i s + ω i
    Figure imgb0038
    to produce signals ω i s + ω i 2 V α - I α * R s 95 , ω i s + ω i 2 V β - I β * R s 114 ;
    Figure imgb0039
    adding the signal ω i s + ω i 2 V β - I β * R s 114
    Figure imgb0040
    to the first intermediate signal (93) and subtracting the signal I α*Lq (118) to produce a signal 1 s + ω i V α - I α * R s + ω i s + ω i 2 V β - I β * R s - I α * L q
    Figure imgb0041
    that corresponds to the first extended rotor flux value (λext_α; 122) and
    subtracting the signal ω i s + ω i 2 V α - I α * R s
    Figure imgb0042
    from the second intermediate signal (110) and subtracting the signal I β*Lq (126) to produce a signal 1 s + ω i V β - I β * R s - ω i s + ω i 2 V α - I α * R s - I β * L q
    Figure imgb0043
    that corresponds to the second extended rotor flux value (λext-β; 130).
  2. The method of claim 1, wherein the selected corner frequency ωi is fixed.
  3. The method of claim 1 or 2, wherein the selected corner frequency ωi is adjustable.
  4. The method of any preceding claim, wherein the step of applying the first extended rotor flux value and the second extended rotor flux value to a phase lock loop to derive an estimated rotor angular position and an estimated rotor angular velocity for the dynamoelectric machine comprises the steps of:
    multiplying the first extended rotor flux value with a sine function feedback signal to produce an α-axis multiplier output signal;
    multiplying the second extended rotor flux value with a cosine function feedback signal to produce an β-axis multiplier output signal;
    subtracting the α-axis multiplier output signal from the β-axis multiplier output signal to produce a difference signal;
    multiplying the difference signal by a proportional and integral regulator function K p + K i s
    Figure imgb0044
    to produce a PI output signal, wherein Kp is a constant value corresponding to a proportional gain of the proportional and integral regulator function, Ki is a constant value corresponding to an integral gain of the proportional and integral regulator function, and s is a Laplace operator;
    multiplying the PI output signal by an integral function 1 s
    Figure imgb0045
    to produce an integration output signal;
    multiplying the integration output signal by a sine function to produce the sine feedback signal; and
    multiplying the integration output signal by a cosine function to produce the cosine feedback signal, wherein the estimated rotor angular position and the estimated rotor angular velocity for the dynamoelectric machine are derived from the proportional and integral regulator function output signal and the integration output signal.
  5. The method of claim 4, further comprising the steps of:
    multiplying the proportional and integral regulator function output signal by a low pass filter function ω c s + ω c
    Figure imgb0046
    to produce the estimated rotor angular velocity ω̂, where ωc is a corner frequency of the low pass filter function;
    generating a delay compensation based on a value of the estimated rotor angular velocity; and
    subtracting the delay compensation from the integration output signal to produce the estimated rotor angular position.
  6. The method as recited in any preceding claim, further comprising the step of monitoring the potentials of the plurality of windings coupled to the stator of the dynamoelectric machine, wherein if the potentials do not exceed a certain threshold, the step of applying the first extended rotor flux value and the second extended rotor flux value to a phase lock loop to derive an estimated rotor angular position and an estimated rotor angular velocity for the dynamoelectric machine is not performed.
  7. The method of any preceding claim, further comprising the step of indicating a fault condition if the rotor angular position for the dynamoelectric machine cannot be determined within a predetermined period of time.
  8. A control for estimating an initial rotor angular position and a rotor angular velocity for a dynamoelectric machine (12) from a standstill comprising:
    a reference frame transformation function for transforming an AC potential (26) for each of a plurality of windings coupled to a stator of the dynamoelectric machine to a stationary frame (α-β) to produce a first transformed potential (V α) and a second transformed potential (Vβ), and
    a phase lock loop (132-158) to derive an estimated rotor angular position (Θ) and an estimated rotor angular velocity for the dynamoelectric machine from the first transformed potential and the second transformed potential;
    wherein the control is arranged to estimate the initial rotor angular position and the rotor angular velocity according to the method of claim 1.
  9. The control of claim 8, wherein if the potential of each of the plurality of windings does not exceed a certain threshold, the control designates the estimated rotor angular position and estimated rotor angular velocity as invalid.
  10. The control of claim 8 or 9, wherein if the rotor angular position for the dynamoelectric machine cannot be determined within a predetermined period of time after a rotating exciter (19) is powered on, the system indicates a fault condition.
  11. The control of claim 8, 9 or 10, wherein if the rotor angular position for the dynamoelectric machine can be determined within a predetermined period of time after a rotating exciter (19) is powered on, an inverter is turned on.
  12. The control of any of claims 8 to 11, wherein the phase lock loop to derive an estimated rotor angular position value and an estimated rotor velocity value for the dynamoelectric machine from the first transformed potential and the second transformed potential comprises:
    a first multiplier (132) for multiplying the first transformed potential with a sine function feedback signal to produce an α-axis multiplier output signal;
    a second multiplier (140) for multiplying the second transformed potential with a cosine function feedback signal to produce an β-axis multiplier output signal;
    a first summer (148) for subtracting the α-axis multiplier output signal from the β-axis multiplier output signal to produce a difference signal;
    a proportional and integral regulator function (152) for multiplying the difference signal by a function K p + K i s
    Figure imgb0047
    to produce a PI output signal, wherein Kp is a constant value corresponding to a proportional gain of the proportional and integral regulator function, Ki is a constant value corresponding to an integral gain of the proportional and integral regulator function, and s is a Laplace operator;
    an integral function (156) for multiplying the PI output signal by an integral function 1 s
    Figure imgb0048
    to produce an integration output signal; s
    a sine function (136) for multiplying the integration output signal by a sine function to produce the sine feedback signal; and
    a cosine function (144) for multiplying the integration output signal by a cosine function to produce the cosine feedback signal, wherein the estimated rotor angular position and the estimated rotor angular velocity for the dynamoelectric machine are derived from the proportional and integral regulator function output signal and the integration output signal.
  13. The control of claim 12, further comprising:
    a low pass filter (160) for filtering the PI output signal by a low pass filter function ω c s + ω c
    Figure imgb0049
    to produce the estimated rotor angular velocity, where ω c is a corner frequency of the low pass filter function;
    a lookup table (164) for generating a delay compensation based on a value of the estimated rotor angular velocity; and
    a second summer (168) for subtracting the delay compensation from the integration output signal to produce the estimated rotor angular position.
EP08251107.2A 2007-05-29 2008-03-27 Method and system for estimating rotor angular position and rotor angular velocity at low speeds or standstill Active EP1998435B1 (en)

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